Here is the much-ballyhooed fuel pump for the M38A1. I finished… - delta_november

May. 3rd, 2007

08:47 am

Here is the much-ballyhooed fuel pump for the M38A1. I finished the rebuild yesterday, and will go and install it on the weekend.

(Click twice for stupid-high resolution)

It's a chunky piece of kit. I'm sure it's bigger than the whole engine on a Vespa. It bolts to the side of the engine block, and the arm on the right side rests on a cam which wiggles it up and down as the engine turns. The top chamber pumps fuel from the tank to the carburetor. The bottom chamber pumps vacuum to run the windshield wipers. There's also some byzantine circuit in there to pressurize the engine crank-case, but I can't say that I fully understand it.

Closing this thing up is pretty final. It's mostly held together with screws. However, just to the left of the arm you can see the pivot pin. The final operation is to whack that several times with a hammer, flaring it out and preventing it from pulling back through the body. One pivot pin comes with each rebuild kit...

Comments:

They're sort of like early Rover wipers. Mounted on the top of the fold-down windshield, they have manual-override levers accessible on the inside. These can be used for a quick mist, and are required to park the wipers out of the way when done with them.